Fan drives

ABSTRACT

A rotary fan including a fluid filled slipping clutch and means for dis-engaging the slipping clutch by means of a remote thermal sensing device in a liquid coolant circuit. In one form of the invention the thermal sensor controls a pneumatic ram connected to a friction clutch in series with the slipping clutch. In another form of the invention the thermal sensor actuates a pneumatic ram in the fan hub which controls a device for evacuating fluid from the slipping clutch to disconnect the drive.

United States Patent 1 91 Elmer Sept. 11, 1973 FAN DRIVES 1,767,5666/1930 Updike 192/55 x 3,145,816 8/1964 Lorean et al. 192/91 A [751Invent: 'F i E 1,667,565 4 1928 Radcliffe 192/58 A pamswlck, Great Bmam2,637,308 5/1953 Dodge 192/82 T ssignee Dyna Nai orth, G a CarnereBritain Primary ExaminerAllan D. Herrmann [22] Filed 1971 Attorney-lrvinS. Thompson et a]. [21] App]. No.: 200,454

' 57 ABSTRACT [30] Foreign Application Priority Data Nov 2 1970 GreatBritain 55 490/70 A rotary fan including a fluid filled slipping clutchand means for dis-engaging the slipping clutch by means of [52] U S Cl192/48 3 192/58 B 192/91 A a remote thermal sensing device in a liquidcoolant cirv 192/82 cuit. in one form of the invention the thermalsensor [51] Int Cl F 47/06 controls a pneumatic ram connected to afriction [58] Fie'ld 58 A 58 B clutch in series with the slippingclutch. In another C 82 91 form of the invention the thermal sensoractuates a pneumatic ram in the fan hub which controls a device [56]References Cited for evacuating fluid from the slipping clutch todisconnect the drive.

5 Claims, 5 Drawing Figures I Patented Sept 11, 1973 2 Sheets-Sheet 1Patnted Sept. 11, 1973 2 Sheets-Sheet 2 FAN DRIVES This inventionrelates to rotary drive units or assemblies for connecting a rotaryinput member to an output member such as a cooling fan. The inventionmay be applied to rotary shaft drives but is particularly applica ble toan actual cooling fan drive assembly as used for example on a motorvehicle or other internal combustion engine.

It is well known that the cooling requirements of any engine on a motorvehicle vary very considerably, and depend amongst other things on theload, gradient, and speed of the vehicle, and the ambient temperatureand wind velocity. Considerable power will frequently be wasted indriving the cooling fan at excessive speed, or when the fan is notrequired at all, for example when the relative wind speed createsadequate ram effect, for cooling purposes. A fan driven at high speedalso creates considerable noise and also tends to cause wear in fanbelts or other drive systems and associated parts such as water pumps.

Many previous attempts have been made to provide some control of thedrive to a fan but most existing systems are expensive or somewhatineffective for one reason or another. It is an object of the presentinvention in particular to provide a fan drive which will allow the fanto be driven when required at a speed somewhat slower than that of theinput drive member, but without incurring the difficulties expected froma normal type of slipping clutch.

Broadly from one aspect the invention consists in a cooling fan driveassembly, comprising a hub for the fan, connected to a rotary drivemember through a viscous slipping clutch arranged in series with athermally controlled positive clutch for interrupting the drive.

The term positive clutch as used above is intended to mean a clutchcapable of being engaged to provide a positive drive, or disengaged tointerrupt the drive. A particularly convenient form of positive clutchis a friction clutch: alternatively an electrically controlled magneticclutch may be used.

According to a preferred feature of the invention the assembly includesa resilient torsional vibration damper in the torsional drive path fromthe drive member to the fan hub. The torsional vibration damper may beon the input side of the slipping clutch, but is preferably situatedbetween the slipping clutch and the fan blades, and according to anotherpreferred feature of the invention the assembly includes remote controlmeans for controlling the engagement of the friction clutch in responseto changes in temperature of a coolant for the engine on which the fanassembly is to be mounted. For example the apparatus may include athermally controlled pneumatic ram mounted on or within the assembly foractuating the friction clutch.

Furthermore the assembly also preferably includes resilient meanstending to urge the friction clutch into an engaged condition, andpreferably the friction clutch is controlled by means of a pneumaticpressure line connected to the assembly at the'end thereof remote fromthe drive member.

Thus the invention provides a simple and entirely automatic system witha combination of features and advantages hitherto unobtainable. Theviscous slipping clutch allows the speed of the fan to vary below thatof the rotary drive member at higher engine speeds and by appropriatedesign the maximum fan speed can be predetermined and set at a valuewhich prevents excessive noise and wear. By combining the viscousslipping clutch in series with a thermally controlled friction clutchthe drive can be totally disconnected when the sensed temperature isabove a preselected minimum value, thus substantially eliminating thewasteful power absorption and heating effect in the slipping clutch forlong periods during operation. With both clutches engaged the torsionalvibrations from the crank-shaft or other drive member are effectivelydamped by the resilient damping device, and the thermal control includesa remote thermal senser which can be associated with the water coolingsystem or other coolant for the engine thus avoiding many of thedifficulties experienced in any system having an air sensing thermaldevice such as a bi-metallic strip exposed directly to the air passingover the engine. Such elements tend to become extremely dirty,inherently have a tendency for thermal drift, and some sluggishness inresponse, and moreover any temperature sensing from cooling air is lessreliable than a liquid coolant thermal sensing system since it isaffected considerably by ambient temperature variations.

From another aspect the invention also consists in a cooling fan driveassembly comprising a hub .forthe fan and a viscous slipping clutchconnected to drive the hub from a rotary drive member, a reservoirforfluid, adjustment means controlling or influencing the displacement offluid between the reservoir andthe slipping clutch to vary the torsionaldrive, and remote control means for actuating the adjustment means, forexample in response to temperature changes at a position displaced fromthe fan.

In such a system the remote control means preferably comprises apneumatic ram forming part of the fan drive assembly, and means forconnection to a nonrotating pneumatic control line.

An assembly according to this latter aspect of the invention has many ofthe same features and advantages mentioned above. By controlling thequantity of fluid effectively present in the slipping clutch the drivecan be varied and by effectively evacuating the clutch the drive can bedisconnected when the sensed temperature so indicates, the temperaturesensing being performed by and through the remote control system from asensing point located for example in the water cooling circuit. Thisassembly may also include a resilient torsional vibration damper actingbetween the fan itself and the rotary drive member to provide orminimise transmission of high frequency vibrations to the fan.

The invention may be performed in various ways and two specificembodiments will now to described by way of example with reference tothe accompanying drawings, in which: i

FIG. 1 is a sectional-side elevation through one half of a first exampleof a fan drive assembly according to the invention, I

FIG. 2 is a diagram illustrating the main components of a remote coolanttemperature sensing control system,

FIG. 3 is a somewhat diagrammatic part-sectional elevation through asecond embodiment, and

FIGS. 4 and 5 are detailed sectional developed views illustrating thetwo operative positions of the fluid scoops incorporated in theembodiment of FIG. 3. p

In the first example the fan drive unit comprises a rdtary drive member10 having bolt holes 11 by which it may be bolted to a drive pulley 9,or some otherdrive shaft such as a crank shaft of the engine. The memberis also-connected to a flange 12 which forms the input element of afriction clutch and to a projecting sleeve element 13 which provides abearing support for the rotary fan hub. The friction clutch inputelement 12 is surrounded by a friction ring 14 of trapezoidalcrosssection, thisbeing surrounded in turn by a friction clutch outputelement 15 attached to the outer housing 18 of a viscous fluid slippingclutch. The housing 18 forms a narrow annular chamber in which islocated a clutch disc 19 having a very small clearance around itsperiphery l7 and on each face, the enclosed chamber being sealed by apair of rotary seals 20, and occupied by a viscous fluid such as asilicone fluid. The disc 19 is attached by bolts 16 to a sleeve 21 whichprovides a hub on which the fan blades 22 are mounted. This sleeve 21 issupported by roller bearings 23 from the sleeve 13 of the input drivemember. The fan blades 22 are attached to a ring 24 which is sandwichedbetween a pair of rubber discs 25, and connected by means of a pressureplate 26 and tension bolts 27 to a flange 28 formed integral with thesleeve 21. It will be seen that the system so far described provides atorsional drive including in series the friction clutch 12, 14, 15, theviscous slipping clutch 18, 19, and the torsional vibration damperconstituted by the rubber mounting 25.

The viscous slipping clutch is permanently filled and sealed and has noexternal control: it automatically drives with increasing slip as theload and speed increase, and may be designed to set a predeterminedmaximum output speed of the fan blades. The friction clutch however iscontrolled by a pneumatic ram assembly built into the fan drive unit andarranged to cause bodily axialmovement of the sleeve 21 relative to theinput drive member 10. Basically this pneumatic ram system comprises acentral stem 30 connected at its right hand, inner, end to the sleeve 13by means of a thrust bearing 31 and attached at its left hand, outer,end by means of a nut 34 to a hollow annular casing or cylinder 32 whichhouses a movable piston 33. The cylinder 32 is provided with a radialcoupling 35 for connection to a flexible compressed air supply line 36(see FIG. 2) by which compressed air is admitted to or exhausted fromthe cylinder through a radial drilling 37 the cylinder 32 and stem 30being fixed axially by means of the bearing 31 and held against rotationby the line 36. An O-ring seal 38 within the cylinder wall engages theexternal surface of the piston. The piston is formed integral with ashort sleeve 40 loosely surrounding the stem 30, and the sleeve 40 isconnected by a thrust bearing 41 to a ring 42 which is secured to theblade mounting sleeve 21, so that axial movements of the piston areimparted to the sleeve 21 and vice versa. A spacer sleeve 43 isinterposed between the sleeve 40 and the inner race of the thrustbearing 31, and a helical compression spring 44 is positioned be,- tweenthe inner race of the bearing 41 and an abutment flange 45 at the righthand end of the spacer sleeve.

When air pressure is admitted through the pressure line 36 and coupling35 the air passes into a chamber 46 on the left side of the piston 33,and since the cylinder 32 is prevented from moving axially by the thrustbearing 31 the air pressure in the ram chamber 46 causes the annularpiston 33 to be displaced to the right in FIG. 1, carrying with it thesleeve 21 and hence the housing 18 and the friction clutch outputelement 15.

This disengages the friction clutch and the drive to the fan is thuscompletely disconnected. The clutch is reengaged by the spring 44 and itwill be noted that this provides a fail safe feature since any failureof the air supply will automatically cause the friction clutch to bere-engaged.

Also it will be noted that both the ram cylinder 32 and the ram piston33 are non-rotary, so that only minimal friction occurs at the O-ringseal 38, regardless of whether the friction clutch is engaged ordisengaged. Furthermore since the clutch engaging spring 44 ispositioned between the inner races of the two thrust bearings 31, 41,and due to the presence of the spacer sleeve 43 between these two races,the force of the spring is not transmitted through these hearings whenthe piston 33 is moved to the right to disengage the friction clutch, sothat the bearings are protected from load during a large part of thelife of the unit.

The casing 18 of the viscous slipping clutch is subject to sometemperature rise due to the inevitable heating of the viscous fluid, andthe casing is provided with a large number ofexternal cooling fins 50exposed to the flow of cooling air passing over' the fan. The rubbermounting rings 25 for the fan blades are however separated from this hotcasing 18 and are only indirectly connected to the internal disc 19, sothat they are effectively protected from any substantial heatingeffects.

As illustrated diagrammatically in FIG. 2 the pneumatic supply line 36is a stationary non-rotating flexible tube which is connected to asupply of compressed air (or vacuum) 52 on the vehicle, via a valve 53mounted on and controlled by. a wax capsule temperature sensing elementfitted into the water cooling circuit of the vehicle, preferably at thelower hose connection 54 to the radiator 55. One form of valve unitdesigned for this purpose is illustrated in US. Pat. No. 3,446,430.

A number of advantages are obtained by the arrangements described. Themaximum power absorption, speed, and noise of the fan are limited by theslipping viscous clutch 18, 19. The slipping clutch drive is howeverover-ridden by the pneumatic thermal control 53 sensitive to the coolanttemperature rather than the air temperature. The slipping clutch is thusfully disconnected when the coolant temperature is above a predeterminedvalue. The torsional vibrations from the input drive member 9 areabsorbed by the resilient rubber damper 25 and are not transferred tothe fan blades so that the unit can, if required, be mounted direct onthe crankshaft, and this is achieved without subjecting the rubbermounting to the heat of the viscous clutch. If the pneumatic controlsystem should fail the friction clutch will re-engage thus providing acontinuous drive through the viscous clutch. Also the thermal drift andthermal delay experienced in any direct air sensing unit are almostentirely eliminated.

In the second example of the invention the unit does not incorporate afriction clutch but has a coolant temperature sensing control system forvarying the effective quantity of liquid in the viscous slipping clutch.As shown in FIG. 3 the unit comprises a main input drive member having aflange 61 formed with holes to receive bolts for connection to acrankshaft or cam shaft of the engine, the drive member 60 beingconnected to an annular drive disc 62 forming the input element of aviscous fluid clutch. The disc is surrounded by a housing comprising aback casting 63 a front plate 64 and an intermediate partition plate 65.The casting 63 and the partition plate 65 are formed to give a smallclearance on both faces of the disc 62 and the space between the plates64 and 65 acts as an internal compartment 67 which provides a fluidreservoir.

The partition plate 65 has a number of small apertures around itsperiphery, and in each of these is mounted an axially movable scoop 70,the scoops being mounted on a control plate 71. When the plate 71 is inthe right hand position illustrated in FIG. 4 the scoops are withdrawninto the apertures in the partition plate, and are ineffective: fluidthen occupies the clearance spaces on both sides of the drive disc 62,and torque is transmitted to the output part of the clutch including theback casting 63 on which the fan blades 75 are mounted. When the plate71 is in its left hand posit-ion illustrated in FIG. 5 the scoops areextended through the apertures in the partition plate into closeproximity with the drive disc 62, and the relative rotation between thedisc and the scoops causes fluid to be impelled radially inwards intothe reservoir compartment 67, passing through apertures 76 in thecontrol plate to occupy the volumes on both sides of this plate 71. Thequantity of fluid in the small clearance volumes on opposite sides ofthe drive disc 62 is thus reduced, so reducing the torque capacity ofthe unit.

The movements of the control plate 71, which govern the operation ofthis viscous drive clutch, are controlled by a remotely situated thermalsensing device similar to the thermal sensing valve 53 of FIG. 2, ar-

ranged to admit compressed air via a flexiblepressure.

line 80 connected to a non-rotary ram cylinder member 81 positionedwithin a central recess in the front plate 64, and axially flxedrelative thereto by a thrust bearing 82. A movable plunger piston 83within the ram cylinder has a pair of O-ring seals engaging the cylinderwall, and the left hand end of this plunger is connected through athrust bearing 84 to a cap 85 which bears on the central part 86 of thecontrol plate. A series of tangential springs 87 are positioned aroundthe periphery of the control plate, and attached to this plate and tothe front plate 64, the springs acting to draw the plate 71 towards thefront plate 64, Le, in a direction to withdraw the scoops 70 so that theoperative clearance spaces of the clutch are allowed to fill with fluid.

In operation, when the temperature of the engine coolant is below thepredetermined value the thermal sensing valve is arranged to connect thepressure line 80 to relief. The springs 87 act to move the plate 71 tothe right, the scoops 70 are withdrawn, fluid occupies the clearancespaces on both sides of the drive disc 62, and the viscous drive unit isallowed to operate in the normal manner, providing a torsional drivewith increased slip as the speed and torsional resistance of the fanblades increase. When the temperature. of the engine coolant reaches thepreselected value the thermal sensing valve connects the pressure line80 to a source of compressed air (as in FIG. 2) which enters the righthand end of the ram cylinder and forces the plunger piston 83 to theleft, thus shifting the control plate 71 in the same direction, and socausing the scoops to extend into close proximity with the drive disc62. As explained this results in fluid being withdrawn from theclearance spaces into the reservoir compartment 67 so that the viscousclutch is rendered partially or wholly inoperative, and the drive to thefan is interrupted. When the coolant temperature falls the process isreversed, the scoops are withdrawn by the springs 87, and the viscousdrive is again rendered operative.

To prevent or reduce transmission of torsional vibrations a rubberdamping unit (not shown) may be incorporated in the drive andconveniently positioned between the housing and the fan blade ring, in asimilar manner to that illustrated in FIG. 1.

I claim:

1. A cooling fan assembly including a rotary input drive member locatedat one axial end of the assembly and formed with means for attachment toa drive shaft or pulley, a friction clutch including a clutch inputelement secured to said input drive member, and a clutch output element,a viscous fluid clutch arranged torsionally in series with said frictionclutch and including arotary clutch casing secured to said frictionclutch output element, and a rotary clutch driven member located withinsaid casing and spaced by a small clearance from the internal wallsurfaces of said casing, and sealing means acting between said clutchcasing and said clutch driven member providing an enclosed sealed fluidchamber, a hub having means for attaching a plurality of fan bladesthereto and secured to said rotary clutch driven member, bearing meansacting between said hub and said input drive member and supporting saidhub for rotation and axial movement relative to said input drive member,a fluid operated ram including two axially movable operative ramelements, namely a ram cylinder and a ram piston, one of said ramelements being connected to said hub and the other ram element beingconnected to said input drive member, whereby relative axialdisplacement of said ram elements causes relative axial displacement ofsaid hub relative to said input drive member, and consequent relativeaxial displacement between said friction clutch input and outputelements, spring means acting in an axial direction between saidfriction clutch input and output elements in a direction to causeengagement of said friction clutch, and a non-rotary pressure fluidsupply conduit located at the end of said hub remote from said rotaryinput drive member, and communicating with said ram cylinder.

2. A cooling fan assembly according to claim 1, wherein said rotaryclutch casing has external cooling fins, and including a resilienttorsional vibration damper element mounted on said hub and interposedbetween said hub and said fan blade mounting means. 3. A cooling fanassembly according to claim 1, wherein said pressure fluid supplyconduit is flexible and is connected to a remote thermally actuatedpressure control valve.

4. A cooling fan ssembly according to claim 1, wherein said twooperative ram elements are both nonrotary and including thrust bearingsacting respectively between one of said ram elements and said fan hub,and between the other of said ram elements and said rotary input drivemember.

5. A cooling fan assembly according to claim 1, wherein said rotaryinput drive member is secured to a rotary drive shaft or pulley, whichconstitutes the sole support for said assembly.

1. A cooling fan assembly including a rotary input drive member locatedat one axial end of the assembly and formed with means for attachment toa drive shaft or pulley, a friction clutch including a clutch inputelement secured to said input drive member, and a clutch output element,a viscous fluid clutch arranged torsionally in ''''series'''' with saidfriction clutch and including a rotary clutch casing secured to saidfriction clutch output element, and a rotary clutch driven memberlocated within said casing and spaced by a small clearance from theinternal wall surfaces of said casing, and sealing means acting betweensaid clutch casing and said clutch driven member providing an enclosedsealed fluid chamber, a hub having means for attaching a plurality offan blades thereto and secured to said rotary clutch driven member,bearing means acting between said hub and said input drive member andsupporting said hub for rotatiOn and axial movement relative to saidinput drive member, a fluid operated ram including two axially movableoperative ram elements, namely a ram cylinder and a ram piston, one ofsaid ram elements being connected to said hub and the other ram elementbeing connected to said input drive member, whereby relative axialdisplacement of said ram elements causes relative axial displacement ofsaid hub relative to said input drive member, and consequent relativeaxial displacement between said friction clutch input and outputelements, spring means acting in an axial direction between saidfriction clutch input and output elements in a direction to causeengagement of said friction clutch, and a non-rotary pressure fluidsupply conduit located at the end of said hub remote from said rotaryinput drive member, and communicating with said ram cylinder.
 2. Acooling fan assembly according to claim 1, wherein said rotary clutchcasing has external cooling fins, and including a resilient torsionalvibration damper element mounted on said hub and interposed between saidhub and said fan blade mounting means.
 3. A cooling fan assemblyaccording to claim 1, wherein said pressure fluid supply conduit isflexible and is connected to a remote thermally actuated pressurecontrol valve.
 4. A cooling fan ssembly according to claim 1, whereinsaid two operative ram elements are both non-rotary and including thrustbearings acting respectively between one of said ram elements and saidfan hub, and between the other of said ram elements and said rotaryinput drive member.
 5. A cooling fan assembly according to claim 1,wherein said rotary input drive member is secured to a rotary driveshaft or pulley, which constitutes the sole support for said assembly.